1. Field of Invention
Gasoline compositions are highly refined products. Despite this, they contain minor amounts of impurities which can promote corrosion during the period that the fuel is transported in bulk or held in storage. Corrosion can also occur in the fuel tank, fuel lines and carburetor of a motor vehicle. As a result, a commercial motor fuel composition must contain a corrosion inhibitor to inhibit or prevent corrosion.
Internal combustion engine design is also undergoing changes to meet new standards for engine exhaust gas emissions. One design change involves the feeding of blow-by gases from the crankcase zone of the engine into the intake air supply to the carburetor rather than venting these gases to the atmosphere as in the past. Another change involves recycling part of the exhaust gases to the combustion zone of the engine in order to minimize objectionable emissions. Both the blow-by gases from the crankcase zone and the recycled exhaust gases contain significant amounts of deposit-forming substances which promote the formation of deposits in and around the throttle plate area of the carburetor. These deposits restrict the flow of air through the carburetor at idle and at low speeds so that an overrich fuel mixture results. This condition produces rough engine idling or stalling causing an increase in the amount of polluting exhaust gas emissions, which the engine design changes were intended to overcome, and also decreases fuel efficiency. The conventional method for overcoming these problems is to employ a detergent fuel additive in commercial motor fuel compositions.
Primary aliphatic hydrocarbon amino alkylene-substituted asparagines are useful as multi-functional fuel additives. They inhibit corrosion as well as exhibit carburetor detergency properties. These asparagines are produced by reacting maleic anhydride with an N-alkylpropane diamine. In actual practice, maleic anhydride is reacted with a mixture of N-alkyl-propanediamines in which the N-alkyl group constitutes a mixture of alkyl radicals having from 12 to 18 carbon atoms. An illustration of this reaction is shown in U.S. Pat. No. 4,207,079 wherein a mixture of N-alkylpropanediamines marketed under the tradename "Duomeen O", is reacted with maleic anhydride to produce the desired primary aliphatic hydrocarbon amino alkylene-substituted asparagines.
In general, a mole of N-alkylpropanediamine is initially reacted with a mole of maleic anhydride dissolved in an organic solvent, such as diluent oil. Following the initial reaction step, the reaction mixture is cooled to a temperature of below 80.degree. C. and a second mole of the N-alkyl-propane-diamine is added to the reaction mixture. The temperature of the reaction mixture is then raised to 100.degree. C. and the mixture heated for two hours. For reasons that are not fully understood but which are believed to be related to impurities in commercial grades of N-alkylpropanediamines, the resulting primary aliphatic hydrocarbon amino alkyl-substituted asparagine is hazy or becomes hazy on standing and often a precipitate forms in the reaction product mixture. The presence of haze or a precipitate in the reaction product precludes its use commercially as an additive in fuels, and is therefore undesirable.
Thus, a need arises for an improved process for reacting maleic anhydride with an N-alkylpropanediamine mixture in the manufacture of an aliphatic hydrocarbon amino alkylene-substituted asparagine product which is not hazy and will not become hazy or form a precipitate on standing.
An object of this invention is to provide an improved process for reacting maleic anhydride with an N-alkyl propane diamines mixture which prevents haze formation or reduces it to an acceptable level in the product. A specific object of this invention is to provide a process for reacting maleic anhydride with an N-alkyl propane diamine mixture in the presence of a phenolic anti-oxidant.
2. Description of the Prior Art
U.S. Pat. No. 4,207,079 discloses a process for making a carburetor detergent and corrosion inhibitor reaction product by reacting maleic anhydride with an N-alkyl alkylene diamine to form a primary aliphatic hydrocarbon amino alkylene substituted asparagine. The process disclosed for making such a reaction product involves suspending the appropriate amount of maleic anhydride in an oil or an inert hydrocarbon solvent such as xylene and then adding the amine to the solution. The disclosure in U.S. Pat. No. 4,207,079 is incorporated herein by reference.
Also U.S. Pat. No. 4,062,874 discloses heat stabilization of maleic anhydride by phenolic compounds.